1. Field of the Invention
The present invention relates generally to an electrically conductive roll used in electrophotographic apparatus such as a copying machine, a printer, or a facsimile machine.
2. Description of the Art
An electrically conductive roll used in electrophotographic apparatus such as a copying machine, a printer, or a facsimile machine may be a developing roll, a charging roll, a transfer roll or the like. The electrically conductive roll may typically have a laminar structure comprising an elastic base rubber layer formed via an adhesive layer on an outer periphery of a core such as a shaft, and further, a surface layer formed on an outer periphery of the elastic base rubber layer. In the case that an addition reaction curing silicone elastomer is used as a material for forming the base rubber layer, a one or two part adhesive mainly comprising silicone rubber or a silane coupling agent each having a vinyl group or a hydrosilyl group, is conventionally applied on an outer periphery of the shaft and then the base rubber layer is formed (see, for example, Japanese Unexamined Patent Publication No. 2002-337161).
However, since the two part adhesive mainly comprising silicone rubber or a silane coupling agent each having a vinyl group or a hydrosilyl group has a short pot life, the adhesive tends to cause adhesive defects when it is allowed to stand for a certain amount of time after mixing. On the other hand, in the case of the one part adhesive mainly comprising silicone rubber or a silane coupling agent each having a vinyl group or a hydrosilyl group, the silane coupling agent thereof may be deactivated by reacting with water in the air and the adhesive may easily be affected by the environment during use. That is, when a base rubber layer is formed on an outer periphery of a metal core after the metal core applied with an adhesive has been stored for a period of time under wet heat conditions, the base rubber layer may exfoliate from the metal core at the interface. In addition, the adhesion of the above-mentioned adhesive greatly depends upon the thickness of the applied adhesive. In other words, when the thickness of the applied adhesive is too thick, exfoliation may easily occur. For this reason, accuracy is required when applying the adhesive, resulting in increased production cost for the rolls.